Coal/cbto

[wind gypsy]

Nope, not always.

If you have a seating die that is primarily making contact way up the nose of the bullet I could see how you can have to greater CTO variance than COAL variance.

 

[mvrk28]

Nope, not always.

You are so far from being correct it's frustrating to even reason with you. The bad part is somebody is going to mistake your council for actual knowledge and they'll waste time doing it the absolute wrong way.

Read the below article (I'd love to see you argue with Bryan Litz):

Effects of Cartridge Over All Length (COAL) and Cartridge Base To Ogive (CBTO) - Part 2

The first half of this article focused on the importance of COAL in terms of SAAMI standards, magazine lengths, etc. There is another measure of length for loaded ammunition which is highly important to precision.

bergerbullets.com

OP,

Please disregard everything this person has said in regards to COAL. Your groups will thank you.

 

[N2TRKYS]

You are so far from being correct it's frustrating to even reason with you. The bad part is somebody is going to mistake your council for actual knowledge and they'll waste time doing it the absolute wrong way.

Read the below article (I'd love to see you argue with Bryan Litz):

Effects of Cartridge Over All Length (COAL) and Cartridge Base To Ogive (CBTO) - Part 2

The first half of this article focused on the importance of COAL in terms of SAAMI standards, magazine lengths, etc. There is another measure of length for loaded ammunition which is highly important to precision.

bergerbullets.com

OP,

Please disregard everything this person has said in regards to COAL. Your groups will thank you.

You’re so closed minded that I feel the same way about you.

Bergers have been the worst example of this issue, which is why I said it’s bullet dependent. You can rely on others to tell you something, or you can check it for yourself.

I prefer to verify things, myself. This is how I know that it isn’t always the case.

 

[Cahunter805]

Nope, not always.

Are you stating that if you loaded some rounds by COAL and then measured the CBTO that both measurements would be just as precise and show the same variances? I have not found this to be true. The exception may be hand turned/cnc lathe turned bullets like a hammer.
I will agree Berger bullets have some inconsistent meplats but nothing a trimmer can’t fix if you wanted to measure them by COAL. They are some of the most consistent if you measure off the Ogive though.
Also I’ve seen some terrible inconsistent polymer tipped bullets Nosler bullets being the worst.

 

[N2TRKYS]

If you have a seating die that is primarily making contact way up the nose of the bullet I could see how you can have to greater CTO variance than COAL variance.

What round to round variance are you getting with the bto?

 

[mvrk28]

You’re so closed minded that I feel the same way about you.

Bergers have been the worst example of this issue, which is why I said it’s bullet dependent. You can rely on others to tell you something, or you can check it for yourself.

I prefer to verify things, myself. This is how I know that it isn’t always the case.

My opinions are based on actual data and research conducted by professional ballisticians and in my own testing with a multitude of bullets over the course of years of reloading. You are flat out wrong, period.

 

[N2TRKYS]

My opinions are based on actual data and research conducted by professional ballisticians and in my own testing with a multitude of bullets over the course of years of reloading. You are flat out wrong, period.

My testing proves that I’m correct with the way I’m doing things. I’m glad what you do works for you.

 

[N2TRKYS]

Are you stating that if you loaded some rounds by COAL and then measured the CBTO that both measurements would be just as precise and show the same variances? I have not found this to be true. The exception may be hand turned/cnc lathe turned bullets like a hammer.
I will agree Berger bullets have some inconsistent meplats but nothing a trimmer can’t fix if you wanted to measure them by COAL. They are some of the most consistent if you measure off the Ogive though.
Also I’ve seen some terrible inconsistent polymer tipped bullets Nosler bullets being the worst.

Noslers have been some of the most consistent bullets for me. The Berger’s are an example of the, not always group. Their inconsistency does require a bto measurement.

Although, their distance to the ogive hasn’t been the best either, in my experience.

 

[MeatBuck]

The confusion I had came from using cnc machined Hammer bullets when I started learning and loading.
When I tried the Berger’s and things were not going as they did with the hammers I assumed the bullets to be out of spec but since I had not had first hand experience with them I figured there could be an issue with equipment. When really it was method that caused the confusion.
The only real issue is mag length. If some of my rounds are too long with consistent cbto I’m stuck hand feeding or having to use a much shorter cbto just to ensure fitment In the mag. With that being the case I think I’m better off single feeding and starting load development just off the lands rather than at mag length with the Berger’s.

Cahunter what kind of bullet trimmer are you talking about? Didn’t know that was a thing.

 

[Brendan]

The only real issue is mag length. If some of my rounds are too long with consistent cbto I’m stuck hand feeding or having to use a much shorter cbto just to ensure fitment In the mag. With that being the case I think I’m better off single feeding and starting load development just off the lands rather than at mag length with the Berger’s.

What you should do in this scenario is know the max COAL your rifle magazine will accept. Then you should find the COAL of a loaded round with the bullets right at the lands (and, see if it fits in the mag). If loaded round at the lands is shorter than your mag, you're all set. Take the CBTO measurement, seat another .010" or what ever you prefer and start with load development. IMO, no need to ever measure COAL again as long as you know the bullets fit in the magazine.

If your COAL is longer than the mag, and you want to mag feed, seat the bullet just deep enough that it'll fit, then switch to CBTO and base your measurements off that for load development going forward.

Do all these tests with dummy rounds / no primer or powder.

 

[Cahunter805]

The confusion I had came from using cnc machined Hammer bullets when I started learning and loading.
When I tried the Berger’s and things were not going as they did with the hammers I assumed the bullets to be out of spec but since I had not had first hand experience with them I figured there could be an issue with equipment. When really it was method that caused the confusion.
The only real issue is mag length. If some of my rounds are too long with consistent cbto I’m stuck hand feeding or having to use a much shorter cbto just to ensure fitment In the mag. With that being the case I think I’m better off single feeding and starting load development just off the lands rather than at mag length with the Berger’s.

Cahunter what kind of bullet trimmer are you talking about? Didn’t know that was a thing.

You can use a Meplat trimmer to uniform the tips of VLD style bullets. You do lose a little BC but nothing major. I personally don’t trim but do drill the tips of Berger’s.

 

[OXN939]

When I tried the Berger’s and things were not going as they did with the hammers I assumed the bullets to be out of spec but since I had not had first hand experience with them I figured there could be an issue with equipment.

This seems reminiscent of the "steel case vs. lacquer coated ammo" debate in ARs and AKs- the problem comes from mixing parts of how things are properly done with one set of components into use with the other. Example- if you stick with bullets like Hammers (or other bullets that have consistent dimensions) when using COAL to find seating depth, you're fine. If you do the same with Bergers or lead soft points that have differing bullet lengths, however, you will likely end up with problems... thus why seating by measurement of CBTO, which works for all bullets, is more frequently recommended. Am I missing anything there?

 

[wind gypsy]

What round to round variance are you getting with the bto?

I don't measure it unless I have reason to believe something is wrong, like say if the seating die leaves a ring mark on the nose of the bullet. BTO is typically within a thou or two if i recall correctly. I've seen it vary by more with heavily compressed loads.

 

[briscoetab]

@OXN939 yea that is how I see it.
Out of curiosity (even though I already knew from previous measurements) I went ahead and measured some of the bullets I had laying around. All I currently had on hand were .264-143 ele-x, .264-140amax, .308-208amax and .224-95smk’s.

This wasn’t super scientific but I think it was good entry get some data. I only measured like 6 of each, wasn’t going to waste a bunch of time. Basically on both the a-max (208 and 140) bullets both the base to ogive and base to tips were within .0015. On the SMK’s, the base to ogive had ES of .001 but the base to tip has ES of .008. For the 143 ele-x the base to ogive had ES of .005 and the base to tip had ES of .009.

The only bullets I had not measured before were the elf-x, I was actually a little surprised with the measurements of the base to ogive.

All of that being said, like stated earlier the ogive is what really matters regardless because it is what sets the distance from the lands, which is what determines the chamber pressure and determines the bullet velocity. I don’t have any evidence on paper for this but in my mind it would make no sense to even test that variability because it is obvious the ogive measurements are what drive velocity. The tip could be off as much as you want but as long as the ogive is in the same position relative to the lands it will creat the same pressure in the chamber/velocity.

I did run some quick numbers in quickload too, for my 6.5 cm with 42.7gn of h4350, 143eld-x. I simply just adjusted the bullet seating depth up and down by .010 it made a difference of 12 FPS. So not much for such a large variability in seating depth. I’ll have to recheck those tomorrow but I think that is right from what I remember.

 

[ShortMountain91]

I agree that CBTO is the way to go but I currently don't have the comparator tool to measure it and have been doing COAL on some 180 accubonds for my 300 wsm. I'm not changing my seating die during a batch and usually the COAL doesn't vary more than +/- .002 . With COAL being so consistent I figured CBTO would be holding about as close. Are y'all seeing big swings in CBTO round to round when keeping the position of the seating die? Are people adjusting every round to hit a CBTO target? Please excuse my ignorance, just getting into reloading

Sent from my SM-G950U using Tapatalk

 

[Lawnboi]

How would you even determine seating depth if not using cbto? Unless just loading to saami coal. Measuring coal without measuring cbto would be a total shot in the dark at your bullet jump.

 

[N2TRKYS]

I don't measure it unless I have reason to believe something is wrong, like say if the seating die leaves a ring mark on the nose of the bullet. BTO is typically within a thou or two if i recall correctly. I've seen it vary by more with heavily compressed loads.

That’s about the difference I’ve seen between the overall bullet lengths and the difference between the base of the bullet to the ogive. Making the difference between using coal and cbto measurement a nonissue.

Of course, if you don’t regularly measure your loaded rounds, you don’t know what yours run.

 

[N2TRKYS]

How would you even determine seating depth if not using cbto? Unless just loading to saami coal. Measuring coal without measuring cbto would be a total shot in the dark at your bullet jump.

Are you talking about your distance to the lands?

 

[MeatBuck]

What you should do in this scenario is know the max COAL your rifle magazine will accept. Then you should find the COAL of a loaded round with the bullets right at the lands (and, see if it fits in the mag). If loaded round at the lands is shorter than your mag, you're all set. Take the CBTO measurement, seat another .010" or what ever you prefer and start with load development. IMO, no need to ever measure COAL again as long as you know the bullets fit in the magazine.

If your COAL is longer than the mag, and you want to mag feed, seat the bullet just deep enough that it'll fit, then switch to CBTO and base your measurements off that for load development going forward.

Do all these tests with dummy rounds / no primer or powder.

Had my smith open the mag box up to fit a coal of 3.080”. He made me some dummies but I disassembled them to shoot the bullet and try out my forester bullet puller.
I’m way past mag length when at lands with either Berger or hammer this being the reason I said I’d just hand feed the Berger’s. The hammers jump far less at mag length .035”ish jump but the Berger’s .105”ish jump.
I say “ish” because my modified case was unfired win brass but I’m now using new Norma and they’re slightly different. I need to have one of my 1x fired pieces of Norma bump sized .002” and threaded for my oal gauge so I can know more exactly where the lands are with these components.
However I’m not shooting Berger’s at any game here in California so I can put off development on them until I get drawn for out of state hunt and just shoot the hammers at mag length as they seem to be impervious to differences in jump. (Steve at hammer will agree with this... as wrong as it sounds).
I’ve gotten the answers and info I needed to resolve my issues at the moment and thank those who replied here.

 

[Lawnboi]

Are you talking about your distance to the lands?

Yes